2003 XJR
Been driving 2-3 days a week with no problems. Drove fine 18 miles to a restaurant. When left immediately ran rough. Throttle seemed to have little to no effect. Pulled over right away. Starts normally, revs a little past 1000, revs drop but goes down to 500 and dies. This has been repeated several times. Right when start can rev past 1000 put then drops and dies. Pedal has no effect as revs drop. Towed home. No CEL or restricted performance. On scanner, no codes and TPS goes from 6 to 100%. Thinking MAF because similar problem on an XJ8 years ago. Cleaned MAF, no effect Is the MAF involved in the initial start up? Suggestions?

 

Disconnect the MAF, it will run if the MAF is bad.

 

My money is on the fuel filter. Seems to be clocked. Replace it.

 

Does this transmission model have a history of the on the transmission body connector getting dirty stalling the engine as the engine / transmission regulate each other ?

The are 2 inside the transmission body speed sensors that need a clean signal coming out

The fault of the speed sensors show in the driveway just coming out of park and low speed at least on the X300 ( different transmission )

 

Filter replace a few thousand miles ago

 

Same with MAF disconnected.

 

Fuel pump; dirty connectors to throttle; bad battery connections; fuel filter, again; sticking temperature sensor

 

Please explain "sticking temperature sensor". You mean for coolant? How is that related? I did notice radiator fan running when think it shouldn't be. Looked at temp gauge and right in middle.

 

Worth using OBD to see if IAT &ECT give plausible values as they're used for air/fuel ratio,

Also could be an air leak, maybe one that comes & goes such as something flexing.

 

You have 1 engine coolant temp sensor ( thermistor ) that feed the engine ECM which in turn controls the fans control relay module so you have a cheap common denominator if that would be enough for the engine being sub par to stall as a not in closed loop engine regulation

Your instrument cluster may not be the same temp sensor as on the inline 6 and is a single wire temp " bulb " not called a sensor by definition

Your closed loop engine coolant temp point is around 165 F and I can be wrong on the V - 8

There is the possibility of the MAF not having the correct AJ27 or abouts on yours vs. the earlier AJ26 engine with a difference on the car side MAF connector pin map or the MAF from earlier AJ26 V - 8

The coolant fans may be correct at low fan speed on initial cold engine just turn key to run before start ( X300 inline 6 had a TSB on this popping the fans fuses causing no fans and overheat ) Bad

 

Did you check the TPS by tapping into the wires(?), or plug in to the DLC and move the pedal? If the later, you got the PPS signal. I ask because the numbers match a PPS. Those TPS's might need a rebuild; I know a place ...

 

Hi packer,

How recently had you purchased fuel prior to the onset of these symptoms? Is it possible you got some fuel contaminated with water? This can clog your fuel filter and/or cause fuel pump death, and any fuel that makes it to the injectors will have trouble igniting.

Typically, the fuel and water get intermixed as it is pumped into your tank, and all may seem normal at first. But over time, sometimes hours or overnight, the denser water settles to the bottom of the tank where it is inhaled by the pump and the problems begin.

Cheers,

Don

 

A clogged water drain line at the fuel cap well can also let water sneak into fuel , just takes a storm or snow fall , this water also gets on the security lock control module connectors ( just underneith well as it flows over ) in which it gives the engine ECM a enable < but it does start .......................

You will see the drain line top cap in the well as you open fill flap

 

I thought on my Foxwell ATP (absolute throttle positon) shows the percentage the throttle plat is open. I guess I could disconnect the TPS and see if I still get a reading.

 

It's on 3/8 tank. Drove all week.

 

Air and coolant temperature match outdoor temperature,

 

Did smoke test - no leaks. Cleaned all connectors to throttle body - no change,
XJR not running - MAF reads 9 g/s. Checked the MAF on my XK8 with car off - MAF reads 399 g/s. I checked the XK8 because expected to see 0 g/s on XJR. Not sure if this means anything.

 

Unplug the MAF & see how it runs. It'll flag a code & the ECU will use a default table to estimate MAF readings enough to run ok. If it runs you've probably found your issue.

 

Starting to sound like the fuel pump; check the fuses. If pump one is out, you should be able to start it from pump two.

As an aside and to answer your question on my first post (although this no longer appears to be your issue): If the temp sensor sends a signal to the ECU via the MAF circuit telling the ECU to either enrich the mixture (for a cold start) or not (for a warm start). Acts like chokes in the old days. If it is bad: you will have either a hard start cold or flooding when warm.

 

You would think so with it saying "absolute." My Autel uses the same labeling and that's what I use to adjust the throttle cable.